Emulsion type resistance reducing agent for shale oil fracturing as well as preparation method and application of emulsion type resistance reducing agent

Abstract

The invention provides an emulsion type resistance reducing agent for shale oil fracturing as well as a preparation method and application of the emulsion type resistance reducing agent. The emulsion type resistance reducing agent for shale oil fracturing is prepared by carrying out inverse emulsion polymerization on monomer raw materials including acrylic acid, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and poly (propylene glycol) monomethacrylate, the total weight of the monomer raw materials is calculated as 100%, and the monomer raw materials comprise 13.5 wt% to 35 wt% of acrylic acid, 50 wt% to 70 wt% of acrylamide, 9.5 wt% to 16.5 wt% of 2-acrylamido-2-methylpropanesulfonic acid and 0.06 wt% to 0.5 wt% of poly (propylene glycol) monomethacrylate. The emulsion type resistance reducing agent for shale oil fracturing has relatively good salt resistance and shearing resistance.

Description

Technical Field

[0001] The present invention belongs to the field of oil and gas field exploitation, and particularly relates to an emulsion-type drag reducer for shale oil fracturing, a preparation method thereof, and an application thereof. Background Art

[0002] The exploitation of unconventional oil and gas resources such as shale oil has become the focus of oil and gas development. Due to its characteristics of low polymer concentration and low viscosity, slickwater has become an important means for shale gas development and fracturing stimulation. Slickwater is composed of water supplemented with various additives, and among them, the drag reducer is the core additive of slickwater. Shale fracturing requires large-displacement volume fracturing. The drag reducer can effectively reduce the flow resistance of the slickwater fracturing fluid in the pipe string, improve the pumping displacement, and at the same time improve the viscosity and sand-carrying capacity of the slickwater fracturing fluid. At present, the drag reducer is mainly polyacrylamide and its derivatives. In areas with limited water resources, it is required to prepare slickwater with high-salt-concentration produced water. The viscosity and drag reduction rate of traditional polyacrylamide drag reducers will be greatly reduced in a high-salt environment. At the same time, traditional polyacrylamide also has characteristics such as poor shear resistance and poor sand-carrying capacity, which severely limit its application. Summary of the Invention

[0003] In order to solve the above problems, the purpose of the present invention is to provide an emulsion-type drag reducer for shale oil fracturing, a preparation method thereof, and an application thereof. The emulsion-type drag reducer for shale oil fracturing has good salt resistance and shear resistance.

[0004] In order to achieve the above purpose, the present invention provides an emulsion-type drag reducer for shale oil fracturing, which is prepared by inverse emulsion polymerization from monomer raw materials including acrylic acid, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and poly(propylene glycol) monomethyl acrylate; calculated based on the total weight of the monomer raw materials being 100%, the monomer raw material composition includes 13.5 wt% - 35 wt% of acrylic acid, 50% - 70% of acrylamide, 9.5 wt% - 16.5 wt% of 2-acrylamido-2-methylpropanesulfonic acid, and 0.06 wt% - 0.5 wt% of poly(propylene glycol) monomethyl acrylate.

[0005] According to a specific embodiment of the present invention, preferably, the raw material polypropylene glycol in the poly(propylene glycol) monomethyl acrylate includes one or a combination of two or more of polypropylene glycol PPG-200, polypropylene glycol PPG-400, polypropylene glycol PPG-1500, polypropylene glycol PPG-2000, and polypropylene glycol PPG-4000. The poly(propylene glycol) monomethyl acrylate can be obtained commercially.

[0006] The present invention also provides a preparation method of the above emulsion-type drag reducer for shale oil fracturing, which includes the following steps:

[0007] (1) Add acrylic acid, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid into water. Under ice bath conditions, adjust the pH to 5.8 - 6.8. Then add a dispersant, a chelating agent, and poly(propylene glycol) monomethyl acrylate. After mixing, obtain the aqueous phase.

[0008] (2) Add an emulsifier into solvent oil. After mixing, obtain the oil phase.

[0009] (3) Add the obtained aqueous phase into the oil phase and emulsify to obtain a reverse emulsion.

[0010] (4) Add an initiator system into the reverse emulsion. After reaction, add a phase inversion agent and stir to obtain the emulsion-type drag reducer for shale oil fracturing.

[0011] According to the specific implementation scheme of the present invention, preferably, the dispersant includes Tween 80 and / or nonylphenol polyoxyethylene ether (OP-10).

[0012] According to the specific implementation scheme of the present invention, preferably, calculated based on the mass of the aqueous phase being 100%, the content of the dispersant is 0.01 wt% - 0.03 wt%.

[0013] According to the specific implementation scheme of the present invention, preferably, the chelating agent includes disodium ethylenediaminetetraacetate and / or VERSENEXTM 80.

[0014] According to the specific implementation scheme of the present invention, preferably, calculated based on the mass of the aqueous phase being 100%, the content of the chelating agent is 0.02 wt% - 0.06 wt%.

[0015] According to the specific implementation scheme of the present invention, preferably, calculated based on the mass of the aqueous phase being 100%, the total content of the monomer raw materials is 35 wt% - 50 wt%.

[0016] According to the specific implementation scheme of the present invention, preferably, the emulsifier is a water-in-oil emulsifier.

[0017] According to the specific implementation scheme of the present invention, preferably, the emulsifier includes one or a combination of two or more of Hypermer A70, Span 80, and Span 60.

[0018] According to the specific implementation scheme of the present invention, preferably, calculated based on the mass of the emulsion-type drag reducer for shale oil fracturing being 100%, the content of the emulsifier is 2 wt% - 5 wt%.

[0019] According to the specific implementation scheme of the present invention, preferably, the solvent oil includes one or a combination of two or more of 3# white oil, 5# white oil, 7# white oil, 10# machine oil, and liquid paraffin.

[0020] According to a specific embodiment of the present invention, preferably, the initiator system is a redox initiator system.

[0021] According to a specific embodiment of the present invention, preferably, the initiator system is a tert-butyl hydroperoxide-sodium metabisulfite system or an ammonium persulfate-sodium bisulfite system.

[0022] According to a specific embodiment of the present invention, preferably, the phase transfer agent includes one or a combination of two or more of AEO-7, AEO-9, OP-10, and NP-10.

[0023] According to a specific embodiment of the present invention, preferably, in step (1), during the pH adjustment process, the temperature is controlled not to exceed 30°C.

[0024] According to a specific embodiment of the present invention, preferably, in step (3), calculated based on the mass of the emulsion-type drag reducer for shale oil fracturing being 100%, the content of the aqueous phase is 50 wt% - 70 wt%, and the content of the oil phase is 30 wt% - 50 wt%.

[0025] According to a specific embodiment of the present invention, preferably, in step (3), the emulsification conditions are emulsification for 2 - 5 minutes at 10000 - 30000 r / min.

[0026] According to a specific embodiment of the present invention, preferably, in step (4), calculated based on the mass of the emulsion-type drag reducer for shale oil fracturing being 100%, the content of the phase transfer agent is 1 - 5 wt%.

[0027] According to a specific embodiment of the present invention, preferably, step (4) includes the following steps:

[0028] The inverse emulsion is controlled at 5 - 15°C, nitrogen is bubbled, an initiator system is added to initiate inverse emulsion polymerization, the addition rate of the initiator system is controlled to keep the polymerization reaction stable at 35 - 40°C, after reacting for 1 - 4 hours, a phase transfer agent is added, and after stirring, the emulsion-type drag reducer for shale oil fracturing is obtained.

[0029] According to a specific embodiment of the present invention, preferably, the tert-butyl hydroperoxide-sodium metabisulfite system is selected as the initiator system.

[0030] According to a specific embodiment of the present invention, preferably, step (4) includes the following steps: controlling the temperature of the inverse emulsion to 5-15 °C, bubbling nitrogen gas, first injecting 0.2-0.4 uL / g of a 1 wt% TBHP (tert-butyl hydroperoxide) solution and a part of a 0.5 wt% MBS (sodium metabisulfite) solution of 0.1-0.3 uL / g into the inverse emulsion to initiate inverse emulsion polymerization, and then adding the remaining 30-60 uL / g of the MBS solution through the pump speed to keep the polymerization reaction stable at 35-40 °C. After reacting for 1-4 h, a phase transfer agent is added and stirred to obtain the emulsion-type drag reducer for shale oil fracturing, wherein the content "uL / g" is calculated based on the mass of the emulsion-type drag reducer for shale oil fracturing.

[0031] According to a specific embodiment of the present invention, the above preparation method includes the following specific steps:

[0032] (1) Add AM, AMPS, and AA to pure water, continuously stir until completely dissolved, and adjust the pH to 5.8-6.8 with an aqueous NaOH solution under ice bath conditions, with the solution temperature not exceeding 30 °C during the process. A dispersant and a chelating agent are added to the solution, continuously stirred evenly, and then poly(propylene glycol) monomethyl acrylate is added, and stirring is continued evenly to complete the preparation of the aqueous phase;

[0033] (2) Add the emulsifier to the solvent oil, continuously stir evenly to complete the preparation of the oil phase;

[0034] (3) Subsequently, slowly add the aqueous phase to the oil phase, continuously stir at a stirring rate of 500 rmp for 20 min, and emulsify with a high-energy emulsifier at a rotation speed of 10,000 rmp for 2 min to complete the preparation of the inverse emulsion;

[0035] (4) Control the temperature of the inverse emulsion to 5-15 °C, bubble nitrogen gas into the emulsion for 30 min, first inject 0.2-0.4 uL / g of a 1 wt% TBHP solution and a part of a 0.5 wt% MBS solution of 0.1-0.3 uL / g into the emulsion to initiate inverse emulsion polymerization, and then add the remaining 50 uL / g of the MBS solution through the pump speed to maintain a heating rate of 0.8 °C / min until the polymerization reaction is stable at 35-40 °C, and the reaction continues for 3 h. Add a phase transfer agent and stir for 2 h to obtain a drag reducer emulsion.

[0036] The present invention also provides the application of the above emulsion-type drag reducer for shale oil fracturing in shale oil fracturing.

[0037] The emulsion-type drag reducer for shale oil fracturing of the present invention is obtained by inverse emulsion polymerization of AM, AA, AMPS and poly(propylene glycol) monomethyl acrylate through a redox initiation system. This drag reducer has excellent salt tolerance, shear resistance and viscoelasticity. The salt-resistant and shear-resistant high-drag-reduction emulsion-type drag reducer of the present invention contributes to the development of oil and gas field production enhancement technology and is of great significance for secondary oil recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is the TEM image of the latex of the emulsion-type drag reducer JZJ-1;

[0039] Figure 2 It is the drag reduction rate curve of 0.05 wt% emulsion-type drag reducer JZJ-1 in clear water or salt water;

[0040] Figure 3 It is the relationship diagram between the apparent viscosity and the shear rate of 0.1 - 0.5 wt% emulsion-type drag reducer JZJ-1;

[0041] Figure 4 It is the relationship diagram between the apparent viscosity and the shear time of 0.05 - 0.5 wt% emulsion-type drag reducer JZJ-1;

[0042] Figure 5 It is the relationship diagram between the modulus and the frequency of 0.1 - 0.5 wt% emulsion drag reducer JZJ-1. DETAILED DESCRIPTION OF THE INVENTION

[0043] For a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solutions of the present invention are described in detail below, but it should not be construed as a limitation of the implementable scope of the present invention.

[0044] Example 1

[0045] This example provides an emulsion-type drag reducer for shale oil fracturing, which is prepared by the following steps:

[0046] (1) Calculated based on the total mass of monomers being 100%, first add 15.4% AMPS, 70% AM, and 14.5% AA to pure water, continuously stir until completely dissolved, and adjust the pH to 6.0 with an aqueous NaOH solution under ice bath conditions; then, calculated based on the total mass of the aqueous phase being 100%, add 0.02% Tween 80 and 0.05% disodium ethylenediaminetetraacetate; finally, calculated based on the total mass of monomers being 100%, add 0.1% of poly(propylene glycol) monomethyl acrylate (the polypropylene glycol part is PPG-400) to complete the preparation of the aqueous phase. Calculated based on the mass of the aqueous phase being 100%, the total content of monomer raw materials is 42%;

[0047] (2) Based on the total mass of the emulsion being 100%, 2% Span 80 was added to No. 7 white oil to complete the preparation of the oil phase. The oil-water mass ratio was 4:6. The aqueous phase was added to the oil phase and stirred at a speed of 500 r / min for 20 min. Then it was transferred to a high-speed emulsifier and emulsified at a speed of 20,000 r / min for 2 min to obtain a reverse emulsion;

[0048] (3) The temperature of the reverse emulsion was controlled at 10 °C, and nitrogen gas was bubbled into the emulsion for 30 min. Then a 1 wt% TBHP solution of 0.3 μL / g and a part of a 0.5 wt% MBS solution of 0.15 μL / g were injected into the emulsion to initiate the reverse emulsion polymerization. The remaining part of the 50 μL / g MBS solution was added through the pump speed to maintain a heating rate of 0.8 °C / min until the polymerization reaction stabilized at 35 - 40 °C, and the reaction continued for 3 h; 3 wt% of OP-10 phase transfer agent (calculated based on the mass of the emulsion-type drag reducer for shale oil fracturing being 100%) was added and stirred for 2 h to obtain an emulsion-type drag reducer, named JZJ-1.

[0049] Comparative Example 1

[0050] This comparative example provides an emulsion-type drag reducer for shale oil fracturing, which is prepared by the following steps:

[0051] (1) Based on the total mass of the monomers being 100%, first 75% AM, 10.5% AMPS, and 14.4% AA were added to pure water and continuously stirred until completely dissolved. Under ice bath conditions, the pH was adjusted to 7.0 with an aqueous NaOH solution, and then 0.1% poly(propylene glycol) monomethyl acrylate (the polypropylene glycol part is PPG-4000) was added. Secondly, based on the total mass of the aqueous phase being 100%, 0.1% Tween 80 and 0.1% disodium ethylenediaminetetraacetate were added to complete the preparation of the aqueous phase. Based on the mass of the aqueous phase being 100%, the total content of the monomer raw materials was 40%;

[0052] (2) Based on the total mass of the emulsion being 100%, 2% Span 80 was added to No. 7 white oil to complete the preparation of the oil phase. The oil-water mass ratio was 4:6. The aqueous phase was added to the oil phase and stirred at a speed of 500 r / min for 20 min. Then it was transferred to a high-speed emulsifier and emulsified at a speed of 10,000 r / min for 1 min to obtain a reverse emulsion;

[0053] (3) The inverse emulsion was controlled at 10 °C, nitrogen gas was bubbled into the emulsion for 30 min, then a 1 wt% TBHP solution of 0.5 μL / g and a partial concentration of 0.1 wt% MBS solution of 0.1 μL / g were injected into the emulsion to initiate inverse emulsion polymerization. The remaining 50 μL / g of the MBS solution was added by pump speed to maintain a heating rate of 0.8 °C / min until the polymerization reaction stabilized at 35 - 40 °C, and the reaction continued for 2 h; 4 wt% of OP-10 phase transfer agent (calculated based on the mass of the emulsion-type drag reducer for shale oil fracturing being 100%) was added and stirred for 5 h to obtain the emulsion-type drag reducer, named DB-1.

[0054] Comparative Example 2

[0055] This comparative example provides an emulsion-type drag reducer for shale oil fracturing, which is prepared by the following steps:

[0056] (1) Calculated based on the total mass of the monomers being 100%, first 75% AM, 15% AMPS, and 9.9% AA were added to pure water and continuously stirred until completely dissolved. Under ice bath conditions, the pH was adjusted to 7.0 with an aqueous NaOH solution, and then 0.1% poly(propylene glycol) monomethyl acrylate (the polypropylene glycol part is PPG-400) was added; secondly, calculated based on the total mass of the aqueous phase being 100%, 0.2% Tween 80 and 0.2% disodium ethylenediaminetetraacetate were added to complete the preparation of the aqueous phase. Calculated based on the mass of the aqueous phase being 100%, the total content of the monomer raw materials was 47%;

[0057] (2) Calculated based on the total mass of the emulsion being 100%, 2% Span 80 was added to No. 7 white oil to complete the preparation of the oil phase. The mass ratio of oil to water was 2:8. The aqueous phase was added to the oil phase and stirred at a speed of 500 r / min for 10 min, and then transferred to a high-speed emulsifier and emulsified at a speed of 20,000 r / min for 1 min to obtain an inverse emulsion;

[0058] (3) The inverse emulsion was controlled at 10 °C, nitrogen gas was bubbled into the emulsion for 30 min, then a 1 wt% TBHP solution of 0.5 μL / g and a partial concentration of 0.5 wt% MBS solution of 0.2 μL / g were injected into the emulsion to initiate inverse emulsion polymerization. The remaining 50 μL / g of the MBS solution was added by pump speed to maintain a heating rate of 0.5 °C / min until the polymerization reaction stabilized at 40 - 45 °C, and the reaction continued for 2 h; 2.5 wt% of OP-10 phase transfer agent (calculated based on the mass of the emulsion-type drag reducer for shale oil fracturing being 100%) was added and stirred for 2 h to obtain the emulsion-type drag reducer, named DB-2.

[0059] Test Example

[0060] The structures and properties of the emulsion-type drag reducers obtained in the above examples and comparative examples were evaluated as follows.

[0061] 1. Microstructure

[0062] The droplet morphology and size of emulsion-type JZJ-1 were observed by transmission electron microscopy, as Figure 1 and shown in Table 1. The polymer latex particles were spherical with regular and uniform morphology, with a maximum particle size of 0.519 μm( Figure 1 as shown in a) below, and a minimum particle size of 218 nm( Figure 1 as shown in b) below, and the average particle size was 368.5 nm. The inverse emulsion polymerization process was stable and there was no particle agglomeration.

[0063] Table 1 Average particle size of different emulsion drag reducers

[0064] Number Average particle size (nm) JZJ-1 368.5 DB-1 472.3 DB-2 407.8

[0065] 2. Measurement of drag reduction rate

[0066] Table 2 shows the drag reduction capabilities of emulsion drag reducers (JZJ-1, DB-1, DB-2) with a concentration of 0.05 wt% in fresh water, 10% NaCl brine, and standard brine (concentration of 85000 ppm): as Figure 2 shown, the maximum drag reduction rate of 0.05 wt% JZJ-1 in fresh water can reach 73%, and then the drag reduction rate stabilizes (measured in accordance with the technical requirements of DB61 / T 1190-2018 Drag reducer for slickwater (emulsion type)); the maximum drag reduction rate in 10% NaCl brine can reach 73%, and the drag reduction rate stabilizes at 72% after 400 s of shear; the drag reduction rate in standard brine slightly decreases, but still stabilizes at about 70%. This indicates that the drag reducer has excellent salt tolerance.

[0067] Table 2 Drag reduction rate test of different drag reducers (drag reducer concentration is 0.05%)

[0068]

[0069]

[0070] 3. Rheological property test

[0071] According to the performance evaluation method of water-based fracturing fluid (SY / T 5107-2016), the viscosities of the drag reducers in the examples and comparative examples were measured at a shear rate of 10 Figure 2 ,

[0070] , , 3 , ,

[0068] ,

[0071] ,

[0067] , , , -1 ,

[0069] , -1 , , , , Figure 3 -10 3 s -1 range. The results are shown in Table 3. Whether at high frequency or low frequency, JZJ-1 has a higher viscosity compared to the comparative examples (DB-1, DB-2). And in the concentration range of 0.1 wt% - 0.5 wt%, the viscosity change of JZJ-1 was measured as Figure 3As shown. At low shear rates, the apparent viscosity of JZJ-1 solutions at various concentrations is around 10 4 mPa·s. As the shear rate gradually increases, the viscosity gradually decreases to 20 mPa·s, indicating that the emulsion-type drag reducer solutions at various concentrations have shear thinning phenomena and are typical pseudoplastic fluids.

[0072] Table 3 Viscosities of Different Drag Reducers (at Different Frequencies, Concentration: 0.1%)

[0073]

[0074] As shown in Table 4, at a shear rate of 170 s -1 , the viscosity changes of the drag reducers in the examples and comparative examples were tested within a shear time of 500 s. Compared with the comparative examples (DB-1, DB-2), JZJ-1 has a higher viscosity, and it was found that the apparent viscosity of JZJ-1 does not show an obvious downward trend at different concentrations (0.05 wt% - 0.5 wt%), as Figure 4 shown. As the shear time progresses, the apparent viscosity will increase to a certain extent at concentrations of 0.2 wt% - 0.5 wt%, confirming that the above emulsion-type drag reducer has excellent shear resistance performance.

[0075] Table 4 Viscosities of Different Drag Reducers (Concentration: 0.05%, Shear Rate: 170 s -1 )

[0076]

[0077] According to the performance evaluation method of water-based fracturing fluids (SY / T 5107-2016), the moduli of the drag reducers in the examples and comparative examples were tested at different frequencies. The results are shown in Table 5. Compared with the comparative examples (DB-1, DB-2), JZJ-1 has higher viscoelasticity both at high frequencies and low frequencies;

[0078] Table 5 Moduli of Different Drag Reducers (Concentration: 0.1%)

[0079]

[0080] It was also found that within the shear frequency range of 0.05 - 10 Hz, the changes of the storage modulus (G') and loss modulus (G'') of JZJ-1 at different concentrations with the shear frequency are as Figure 5 shown. Both G' and G'' increase with the increase in the concentration of the drag reducer, indicating that the higher the concentration of the drag reducer solution, the more obvious its viscoelasticity. Within the shear frequency of 10 Hz, for the drag reducer solutions with concentrations of 0.1 - 0.5%, G' > G'', and the solutions show excellent elasticity.

Claims

1. An emulsion-type drag reducer for shale oil fracturing, which is prepared by inverse emulsion polymerization from monomer raw materials including acrylic acid, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and poly(propylene glycol) monomethyl acrylate; Calculated based on the total weight of the monomer raw materials being 100%, the monomer raw material composition includes 13.5 wt% - 35 wt% of acrylic acid, 50% - 70% of acrylamide, 9.5 wt% - 16.5 wt% of 2-acrylamido-2-methylpropanesulfonic acid, and 0.06 wt% - 0.5 wt% of poly(propylene glycol) monomethyl acrylate.

2. The emulsion type drag reducer for shale oil fracturing according to claim 1, wherein, The raw material polypropylene glycol in the poly(propylene glycol) monomethyl acrylate includes one or a combination of two or more of polypropylene glycol PPG-200, polypropylene glycol PPG-400, polypropylene glycol PPG-1500, polypropylene glycol PPG-2000, and polypropylene glycol PPG-4000.

3. A preparation method of the emulsion-type drag reducer for shale oil fracturing according to claim 1 or 2, which includes the following steps: (1) Add acrylic acid, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid to water, adjust the pH to 5.8 - 6.8 under ice bath conditions, add a dispersant, a chelating agent, and poly(propylene glycol) monomethyl acrylate, and obtain an aqueous phase after mixing; (2) Add an emulsifier to solvent oil, and obtain an oil phase after mixing; (3) Add the obtained aqueous phase to the oil phase, emulsify, and obtain an inverse emulsion; (4) Add an initiator system to the inverse emulsion, after the reaction, add a phase transfer agent, and stir to obtain the emulsion-type drag reducer for shale oil fracturing.

4. The preparation method according to claim 3, wherein The dispersant includes Tween 80 and / or nonylphenol polyoxyethylene ether; Preferably, calculated based on the mass of the aqueous phase being 100%, the content of the dispersant is 0.01 wt% - 0.03 wt%.

5. The preparation method according to claim 3, wherein, The chelating agent includes disodium ethylenediaminetetraacetate and / or VERSENEX™ 80; Preferably, calculated based on the mass of the aqueous phase being 100%, the content of the chelating agent is 0.02 wt% - 0.06 wt%.

6. The preparation method according to claim 3, wherein, Calculated based on the mass of the aqueous phase being 100%, the total content of the monomer raw materials is 35 wt% - 50 wt%.

7. According to the preparation method described in claim 3, wherein, The emulsifier is a water-in-oil emulsifier, preferably including one or a combination of two or more of Hypermer A70, Span 80, and Span 60; Preferably, calculated based on the mass of the emulsion-type drag reducer for shale oil fracturing being 100%, the content of the emulsifier is 2 wt% - 5 wt%.

8. The preparation method according to claim 3, wherein, The solvent oil includes one or a combination of two or more of 3# white oil, 5# white oil, 7# white oil, 10# machine oil, and liquid paraffin.

9. The preparation method according to claim 3, wherein, The initiator system is a redox initiator system, preferably a tert-butyl hydroperoxide-sodium metabisulfite system or an ammonium persulfate-sodium bisulfite system.

10. The preparation method according to claim 3, wherein, The phase transfer agent includes one or a combination of two or more of AEO-7, AEO-9, OP-10, and NP-10.

11. The preparation method according to claim 3, wherein, In step (1), control the temperature not to exceed 30°C during the pH adjustment process.

12. The preparation method according to claim 3, wherein, In step (3), calculated based on the mass of the emulsion-type drag reducer for shale oil fracturing being 100%, the content of the aqueous phase is 50wt%-70wt%, and the content of the oil phase is 30wt%-50wt%.

13. The preparation method according to claim 3, wherein, In step (4), calculated based on the mass of the emulsion-type drag reducer for shale oil fracturing being 100%, the content of the phase inversion agent is 1-5wt%.

14. The preparation method according to claim 3, wherein, Step (4) includes the following steps: Controlling the temperature of the inverse emulsion to 5-15°C, bubbling nitrogen, adding an initiator system to initiate inverse emulsion polymerization, controlling the addition rate of the initiator system to keep the polymerization reaction stable at 35-40°C, after reacting for 1-4h, adding a phase inversion agent, and stirring to obtain the emulsion-type drag reducer for shale oil fracturing; Preferably, step (4) includes the following steps: Controlling the temperature of the inverse emulsion to 5-15°C, bubbling nitrogen, first injecting 0.2-0.4 μL / g of a 1wt% concentration of tert-butyl hydroperoxide solution and 0.1-0.3 uL / g of a partial concentration of 0.5wt% concentration of sodium metabisulfite solution into the inverse emulsion to initiate inverse emulsion polymerization, and then adding the remaining 30-60 uL / g of sodium metabisulfite solution through the pump speed to keep the polymerization reaction stable at 35-40°C, after reacting for 1-4h, adding a phase inversion agent, and stirring to obtain the emulsion-type drag reducer for shale oil fracturing.

15. Use of the emulsion-type drag reducer for shale oil fracturing according to claim 1 or 2 in shale oil fracturing.

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